Project “Why is the deep Arctic Ocean Warming? (WAOW)”, funded by Vetenskapsrådet grant 2018-03859
Ca 4 million SEK; I was the PI (single applicant; early career grant)
Started in January 2019, finished in December 2024

The aim of this project was to finally determine the path and variability of the deep waters of the Arctic Ocean, from 2000 m to the sea floor, using notably data that we collected during the international MOSAiC expedition (2020) and the Synoptic Arctic Survey (2021). But covid19 happened, so data releases were delayed. And Russia invaded Ukraine so we had to stop collaborating with Russian researchers, so we lost any possibility to study the dense water overflows. At least the climate models did not disappoint.

Team:

• Myself – this research area is my primary focus;
• PhD student Salar Karam, of which I was the main supervisor, October 2019 to June 2024. He successfully defended in June 2024.
• Olli Huhn and Maren Walters from Uni Bremen, for expertise with CFC analysis;
• Collaboration with the wider MOSAiC Team Ocean and the Swedish Synoptic Arctic Survey consortium.

Publications:

• Salar’s PhD thesis: “High-resolution dynamics of the deep Arctic Ocean: From thin meltwater layers to large-scale transport”, comprising papers Heuzé et al. (2023), Smith et al. (2023), Karam et al. (2023), and Karam et al. (2024).
• Description paper of our MOSAiC transient tracer data sets (Heuzé et al., 2024).
• Quantification of water mass exchanges between the two deep Arctic basins, highlighting the role and ubiquity of deep eddies, led by my PhD student Salar Karam (Karam et al., 2023) .
• Assessment of biases in the modelled Arctic Ocean (Heuzé et al., 2023) and consequences on predictions of its changes (Muilwijk et al., 2023, Heuzé and Liu, 2024). The release of these studies generated a lot of media attention from 13th March 2023.
• Collaboration with biologists, where we show a clear relationship in the central Arctic between water masses and ecosystem abundance and diversity (Snoeijs-Lejonmalm et al., 2022, Vermassen et al., 2025).
• Overviews of the MOSAiC expedition: Atmosphere (Shupe et al., 2022), Snow and Sea Ice (Nicolaus et al., 2022), Physical Oceanography (Rabe et al., 2022), Distributed Network (Rabe et al., 2024), Ecosystem (Fong et al., 2024).
• Review of the state of the Arctic Ocean, highlighting changes in the freshwater cycle and which components of the climate system are still too poorly observed to conclude (Solomon et al., 2021).

Datasets generated by this team:

• MOSAiC, transient tracer and noble gases in the ocean: https://doi.pangaea.de/10.1594/PANGAEA.961729
• MOSAiC, transient tracer and noble gases in the snow: https://doi.pangaea.de/10.1594/PANGAEA.961738
• MOSAiC, ship CTD, sensor data: https://doi.pangaea.de/10.1594/PANGAEA.959963
• MOSAiC, ship CTD, bottle data: https://doi.pangaea.de/10.1594/PANGAEA.959965
• MOSAiC, on-ice CTD “Ocean City”, sensor data: https://doi.pangaea.de/10.1594/PANGAEA.959964
• MOSAiC, on-ice CTD “Ocean City”, bottle data: https://doi.pangaea.de/10.1594/PANGAEA.959966
• Synoptic Arctic Survey, CTD, sensor data: https://doi.pangaea.de/10.1594/PANGAEA.951266
• Synoptic Arctic Survey, CTD, bottle data: https://doi.pangaea.de/10.1594/PANGAEA.951264

Conference, seminar, or outreach presentations related to this project:

• 15-17 May 2024, Swedish Climate Symposium, Norrköping (Sweden)
  Céline Heuzé, talk: No emergence of deep convection in the Arctic Ocean across CMIP6 models
• 15-19 April 2024, EGU24, Vienna (Austria)
  Céline Heuzé, convenor of session OS1.1 “Changes in the Arctic Ocean, sea ice and subarctic seas systems: Observations, Models and Perspectives”
  and poster: No emergence of deep convection in the Arctic Ocean across CMIP6 models
• 26-29 February 2024, International MOSAiC Science Conference, Potsdam (Germany)
  Céline Heuzé, Keynote speaker: Ocean overview
  and convenor of the TRACERS session
  and talk: A year of transient tracers (chlorofluorocarbon 12 and sulfur hexafluoride), noble gases (helium and neon), and tritium in the Arctic Ocean from the MOSAiC expedition (2019–2020)
• 18-23 February 2024, Ocean Sciences Meeting, New Orleans (US)
  Salar Karam, talk: Continued warming of deep waters in Fram Strait
• 7 February 2024, UNIS (Svalbard)
  Céline Heuzé, seminar: The deep Arctic Ocean – not as isolated as you’d think
• 12 December 2023, Sea and Society Day, Göteborg (Sweden)
  Céline Heuzé, invited talk: The changing Arctic Ocean
• 6-9 November 2023, Nansen Legacy international conference, Tromsø (Norway)
  Céline Heuzé, convenor of the plenary session “The Future Arctic Ocean”
  and poster: Can we even predict the future Arctic Ocean?
• 3-4 October 2023, “Science Opportunities on Polar Connect” workshop, Oslo (Norway)
  Céline Heuzé, invited talk: Key challenges in Arctic oceanography
• 28-29 September 2023, “CMIP6 models in the Arctic” workshop, Bergen (Norway)
  Céline Heuzé, invited talk: The Arctic Ocean in CMIP6 models: historical biases
• 11-20 July 2023, IUGG Berlin (Germany);
  Céline Heuzé, keynote talk: Modelling the Arctic Ocean – a non-exhaustive review
• 5 May 2023, University of East Anglia (UK)
  Salar Karam, invited seminar: Critically important, yet forgotten: thin and transient meltwater layers and false bottoms in the Arctic sea ice pack
• 4 May 2023, Sweco Göteborg (Sweden)
  Céline Heuzé, invited talk: Varför borde *du* bry dig om Arktis?
• 18 April 2023, University of Bremen (Germany)
  Céline Heuzé, seminar: The deep Arctic Ocean – not as isolated as you’d think
• 30 March 2023, University of Gothenburg (Sweden)
  Salar Karam, seminar: Deep ocean dynamics in the Arctic Ocean
• 5-10 March 2023, Gordon Research Conference on Polar Marine Science, Ventura (US)
  Salar Karam, poster: Bottom temperature data observed from autonomous buoys deployed during MOSAiC
• 13-17 February 2023, MOSAiC Science Conference, Boulder (US)
  Salar Karam, poster: Bottom temperature data observed from autonomous buoys deployed during MOSAiC
• 23-27 May 2022, EGU22, Vienna (Austria)
  Céline Heuzé, award lecture: Global deep waters: what we know, what we know we do not know, and what we should do about it
  Céline Heuzé, talk: Large biases in hydrography and circulation of the Arctic Ocean in CMIP6 models
• 16-18 May 2022, Swedish Climate Symposium, Norrköping (Sweden)
  Céline Heuzé, talk: Large biases in hydrography and circulation of the Arctic Ocean in CMIP6 models
• 25-29 April 2022, International MOSAiC Science Conference/Workshop, Potsdam (Germany)
  Céline Heuzé, plenary talk: OCEAN overview
  Céline Heuzé, talk: Water mass history from transient tracers to map species movements
  Salar Karam, poster: Observations of a Freshwater Lens during MOSAiC
• 28 October 2021, Geoseminar, Göteborgs University (Sweden)
  Céline Heuzé, seminar: Why is the Arctic Ocean so wrong in CMIP models?
• 20 October 2021, MOSAiC’s Team ECO workshop (online)
  Céline Heuzé, requested talk: Physical Oceanography during MOSAiC: first results
• 12 October 2021, ArcTrain annual meeting (online)
  Céline Heuzé, invited lecture: Why is the Arctic so wrong in CMIP models?
• 19-30 April 2021, EGU21 (online)
  Salar Karam, talk: Recirculation of Canadian Basin Deep Water in the Amundsen Basin
• 2 February 2021, Arctic Frontiers (online)
  Céline Heuzé, keynote presentation: The first full-depth hydrography of the Eurasian basin
• 9 December 2020, APECS Sweden mini-conference, Göteborg (Sweden)
  Salar Karam, talk: Conducting field work during a pandemic
• 1 October 2020, US IARPC (online)
  Céline Heuzé, requested talk: Physical Oceanography during MOSAiC – an overview
• 24 January 2020, Lamont Doherty Earth Observatory (online)
  Céline Heuzé, seminar: Deep waters: what we know, what we do not know and what we are doing about it
• 22 October 2019, Fonster mot naturvetenskap, Göteborg (Sweden)
  Céline Heuzé, talk: Livet ombord en isbrytare… utan internet
• 4 October 2019, University of East Anglia (UK)
  Céline Heuzé, seminar: Deep waters: what we know, what we do not know and what we are doing about it. (a.k.a. “Big Boats and Big Data”)